Alipally1, I use a completely opposite trick LOL! I found that when I made some general assertion about how things are ("time to go home from the park now", "we can't afford that") then they argue against that ("no it isn't", "you do have money, I saw you with some earlier").
Instead, whenever possible I frame it in terms of my own feelings and needs: "I'm cold. I want to go home", "I want to save my money for something else". It took me a while to get used to, because as a parent I was pretending I had no needs of my own and everything was about the children.
But this works better for me. How can a kid argue when mum says she's cold? It turns their attention away from themselves and towards other people. Occasionally they come up with alternative solutions which make everyone happy: "Could you get yourself a cup of tea from the kiosk - would you want to stay longer then?" It feels more honest too.
I think it may help them communicate better as they get older, because they can explain what the real issue is. So yesterday dd's friend wanted to borrow her spade and instead of saying, "No, it's mine" she said "I'm worried that you'll leave it in the sandpit and some toddler will go off with it like they always do." Friend promised to keep the spade with her continuously and return it to dd when she was finished, and I promised to keep an eye on it too.